Cause: Service may be unavailable or Network connectivity may have been compromised.Resolution:Verify all Web Conferencing Edge Services in the topology are running, and network connectivity is available.

External Users also reported that couldn’t use WhiteBoard, Polls, Q&A or present PowerPoint with the following errors messages:

We can’t connect to the server for sharing right now.

Network issues are keeping you from sharing notes and presenting whiteboards, polls and uploaded PowerPoint files.

While this is still being investigated a KB article was release with the current workarounds:

This .NET Framework update adds an additional check to the certificate on Enhanced Key Usage (EKU), since all Lync/SfB Server by default use Web Server template, they will only have the Server Authentication in the EKU.

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I get the following Error after trying to sign a Certificate with the duplicate template:
0x80094802 (-2146875390 CERTSRV_E_TEMPLATE_CONFLICT)
Denied by Policy Module 0x80094802, The request specifies conflicting certificate templates: WebServer/WebServerClientandServer

This is good article… issue was fixed once i applied workaround 2….. after 1 week once i deploy old topology… the issue occur again…i tried to repeat the same work around 2… the issue not fixed now… can you please help me

Central Logging had entries like this one at the time stamp the web app:
TL_ERROR(TF_COMPONENT) [\]251C.7EB8:: (LDM,TLSTransport.TraceSocketWithException:tlstransport.cs(173)) (00000000024DEA1F)Caught exception for connection :8060: System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.
at System.Net.Security.SslState.EndProcessAuthentication(IAsyncResult result)
at Microsoft.Rtc.Server.DataMCU.Transports.TLSTransport.Sync_DotNetAuthComplete(IAsyncResult asyncResult)

What i did to resolve this was to also re-issue the Front End Default certificate based on the WebServerClientandServer template and restart SfB services on the Front End.
(Stop-CSWindowsService / Start-CSWindowsService).

Got the new internal certs deployed ok, but now I am getting an error on the Lync Edge server:

Web Conferencing Server connection failed to establish.

Over the past 1 minutes Lync Server as experienced incoming TLS connection failures 1 time(s). The error code of the last failure is 0x80090331 (The client and server cannot communicate, because they do not possess a common algorithm.
) and the last connection was from the host “”.
Cause: This can occur if this box is not properly configured for TLS communications with remote Web Conferencing Server.
Resolution:
Check your topology configuration to ensure that both this host and remote Web Conferencing Server can validate each other TLS certificates and are otherwise trusted for communications.

I’ve doubled checked (not that it should of changed) that the internal Root CA cert is still in the Trusted Root.

Hi!
I have similar error on multiple SfB environments with the same Event ID 41029 (please see below) However the first time discovered on the server was in February this year. Interesting is the port is opened and the webapp prezentation works well. Do you think might this error anything to do with the 41026?

Also, verified the EKU – in all Sfb environment is Server and Client authentication.

The 41026 is the event that reports the connectivity loss, however, other issues can cause the event.
Regarding this one, I would check if the everything is OK regarding the certificate store placement. .
Sometimes this is also associated to the LyncExtReach application pool, by default, this App Pool is configured to “onDemand”.